Maryland Borders: States, Map & Complete Guide
Fact-checked • Updated January 11, 2026
Maryland borders four states: Pennsylvania to the north, Delaware to the east, Virginia to the south, and West Virginia to the west. The state also meets the Atlantic Ocean along its eastern shore and surrounds most of the Chesapeake Bay. The Potomac River forms much of Maryland's southern and western borders with Virginia and West Virginia.
Maryland Border Map
Map showing Maryland's boundaries with four states, the Atlantic Ocean, and Chesapeake Bay.
Border Details
Explore each of Maryland's borders in detail. Click any card to learn more.
Pennsylvania
Pennsylvania forms Maryland's entire northern border.
Delaware
Delaware borders Maryland's eastern shore on the Delmarva Peninsula.
Virginia
The Potomac River forms most of Maryland's border with Virginia.
West Virginia
The Potomac River creates Maryland's border with West Virginia.
Atlantic Ocean
The Atlantic Ocean borders Maryland's eastern shore.
Chesapeake Bay
The Chesapeake Bay divides Maryland into two regions.
Which States Border Maryland?
Maryland shares its borders with four U.S. states: Pennsylvania to the north, Delaware to the east, Virginia to the south, and West Virginia to the west. The Potomac River forms much of Maryland's borders with both Virginia and West Virginia.
North: Pennsylvania (Mason-Dixon Line)
Pennsylvania and Maryland are separated by a border located on Maryland's northern edge. This boundary is the famous Mason-Dixon Line, surveyed in the 1760s to settle a border dispute between the colonies.
The Maryland-Pennsylvania border extends for about 230 miles from West Virginia in the west to Delaware in the east. The border runs roughly east-west along the 39°43' north parallel. Maryland counties along this border include Garrett, Allegany, Washington, Frederick, Carroll, Baltimore, Harford, and Cecil. The Mason-Dixon Line historically divided the North from the South and free states from slave states before the Civil War.
- About 230 miles, the Mason-Dixon Line
- Historic dividing line between North and South
- Maryland counties: Garrett, Allegany, Washington, Frederick, Carroll, Baltimore, Harford, Cecil
East: Delaware (Delmarva Peninsula)
Delaware and Maryland are separated by a border located on Maryland's eastern side. The boundary runs roughly north-south through the Delmarva Peninsula, which Maryland shares with Delaware and Virginia.
The Maryland-Delaware border extends for about 125 miles from Pennsylvania in the north to the Atlantic Ocean in the south. The border includes both straight survey lines and the Transpeninsular Line. Maryland counties along this border include Cecil, Kent, Caroline, Dorchester, Wicomico, and Worcester. The border divides the Delmarva Peninsula between the two states.
- About 125 miles on Delmarva Peninsula
- North-south through Eastern Shore
- Maryland counties: Cecil, Kent, Caroline, Dorchester, Wicomico, Worcester
South: Virginia (Potomac River Border)
Virginia and Maryland are separated by a border that includes both the Potomac River and a land boundary on the Delmarva Peninsula. The Potomac River forms the border from Washington, D.C. westward, while a land border exists on the Eastern Shore.
The Maryland-Virginia border extends for about 200 miles total. The Potomac River creates most of this boundary, with the border following the southern shore of the river (meaning the entire Potomac River belongs to Maryland). On the Eastern Shore, a land border divides the Delmarva Peninsula. Maryland counties along this border include Montgomery, Prince George's, Charles, St. Mary's, Worcester, and Somerset. Major cities near this border include Washington, D.C., which sits on the Maryland-Virginia border.
- About 200 miles total
- Potomac River forms western section
- Land border on Eastern Shore
West: West Virginia (Potomac River Border)
West Virginia and Maryland are separated entirely by the Potomac River along Maryland's western edge. The river creates a natural boundary through the Appalachian Mountains.
The Maryland-West Virginia border extends for about 180 miles along the Potomac River from Pennsylvania in the north to Virginia in the south. The border follows the southern bank of the Potomac River. Only two Maryland counties touch this border: Garrett and Allegany. The border region is mountainous and includes parts of the Appalachian range.
- About 180 miles along Potomac River
- Entire border formed by river
- Maryland counties: Garrett, Allegany only
Chesapeake Bay: Dividing Maryland in Two
The Chesapeake Bay is North America's largest estuary and divides Maryland into two distinct regions: the Western Shore and the Eastern Shore. The bay runs roughly north-south through the center of Maryland for about 195 miles within state boundaries. While the Chesapeake Bay is not a border with another state, it creates a dramatic geographic division within Maryland. The bay is about 4 to 30 miles wide in Maryland, and the Chesapeake Bay Bridge connects the two shores. Maryland surrounds most of the Chesapeake Bay, with Virginia bordering the southern portion.
Atlantic Ocean Coastline
The Atlantic Ocean borders Maryland's eastern shore along the Delmarva Peninsula for about 31 miles. This coastline includes the popular beach resort of Ocean City and Assateague Island, famous for its wild horses. While Maryland's ocean coastline is relatively short, the state's total tidal shoreline (including the Chesapeake Bay and all inlets) extends for over 3,190 miles.
Potomac River: Maryland's Southern and Western Border
The Potomac River forms Maryland's entire border with both Virginia (western section) and West Virginia, running for about 380 miles total. Uniquely, the entire Potomac River belongs to Maryland rather than being divided down the middle—Maryland's border is defined as the low-water mark on the Virginia and West Virginia shores. This means Maryland owns the river and has jurisdiction over it, a result of colonial-era land grants. The nation's capital, Washington, D.C., sits on the northern bank of the Potomac River between Maryland and Virginia.
Maryland's Unusual Shape
Maryland has one of the most irregular shapes of any U.S. state. The Chesapeake Bay divides the state into two parts, creating the distinctive Eastern Shore region. Additionally, the state extends westward in a narrow panhandle that's only about 2 miles wide at its narrowest point near Hancock. This unusual geography results from colonial-era boundary disputes and the Potomac River's course. Maryland completely surrounds Washington, D.C. on three sides, and the state's shape has been described as resembling a crab—fitting for a state famous for blue crabs.
Key Facts & Statistics
This table shows every border Maryland shares, organized by direction and type.
Maryland borders exactly four U.S. states
Frequently Asked Questions
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Sources & References
This article has been researched using authoritative sources to ensure accuracy and reliability.
Geographic features, river boundaries, and topographic data
Chesapeake Bay and Atlantic coastline data